Universal planetary clamping device

ABSTRACT

A rigid plate having a work piece supporting surface is securable to a machine tool. A plurality of spindles, each rotatable about an axis perpendicular to the support surface, are journalled within the plate. Engagement means carried by each spindle detachably receive attachment means for affixing a work piece to the supporting surface. The location of each engagement means is moveable relative the supporting surface in response to rotation of the respective spindle.

This invention relates to machine tools.

More particularly, the instant invention concerns accessories andattachments for machine tools.

In a further aspect, the present invention concerns a fixture forholding a work piece during machining operations.

Various methods are well known for fabricating an article from rawmaterial. Broadly, commercial and industrial fabricating processes canbe classified under the headings of machining, forming and assembling.Of immediate concern, is the procedure of machining.

In general, machining can be defined as the act of or the processesinvolved in shaping a solid piece of raw material into a finishedproduct, usually in accordance with a predetermined plan as may be givenby a blueprint. The material being worked upon is usually referred to asthe work piece. During machining, various cutting operations areperformed upon the work piece by a machine tool. Common machiningoperations include drilling, turning, boring, grinding, shaping, planingand other well known material removing procedures. The actual removal ofmaterial is done by a cutting tool which is held and driven by a machinetool, such as a drill press, lathe, vertical and horizontal millingmachines, surface grinder, internal and external grinders, shaper andplaner. Other machine tools and cutting processes will readily occur tothose skilled in the art.

The prior art is replete with clamping and holding devices forsupporting a work piece during machining. Face plates, chucks andcullets are used to hold the work piece for lathes and other machinetools in which the work piece is rotated against a stationary cuttingtool. Angle plates, vises and various hold-down and clampingarrangements are commonly used to secure work in machine tools of thetype having a rotating cutter. Milling machines and similar machiningtools have integral work supporting tables, while in machines of thetype represented by lathes, the work supporting device is attached to aspindle.

Each type of work supporting fixture has unique, inherentcharacteristics which are especially suited for particular machiningoperations. Vises and chucks grip a portion of the work piece which isthen unavailable for machining. Face plates and angle plates can be madeto support work in such a manner that substantial portions of the workpiece are exposed. Numerous means are commonly employed within the artfor securing the work piece to a plate-type holding fixture. Forexample, clamps may embrace the work piece and in turn be secured to theplate by bolts received directly in tapped holes within the plate, orengaged with T-nuts carried in especially machined slots which extendalong the surface of the plate.

Another arrangement includes the use of C-clamps or parallel clampsstraddling both the work piece and the plate for abutting the work pieceagainst the surface of the plate.

For production machining it is common practice to provide a face platehaving a plurality of apertures, either slots or cylindrical bores,extending therethrough. The work piece, usually a rough cast or moldeditem, is preliminarily prepared by machining a flat surface which thenbecomes the base or reference surface. Threaded holes, normally made bydrilling and tapping, are formed into the work piece from the machinedsurface. To provide adequate support, two or more threaded holes may becreated. The machined surface of the work piece is then placed againstthe work supporting surface of the plate. Subsequently, bolts are passedthrough the apertures in the plate and threadedly engaged within thepreformed holes in the work piece. Locating fixtures of various typesare commonly used to maintain relative positioning between subsequentwork pieces to enable machining operations to be accomplished withoutresetting the machine.

The latter method of attaching a work piece to a face plate has obviousadvantages over clamping type methods. A substantially greater portionof the work piece is available for machining. However, it is physicallyimpossible to provide a plate having an infinite array of apertures.Therefore, the holes drilled and tapped into the work piece must beaccurately located to align with pre-existing apertures within the plateor apertures especially created for the immediate purpose. Whenconsidering a large production run, the accurate location of severalthreaded holes within the work piece is a slow laborious task presentingundue financial burden upon the manufacturer. This is especially truewhen considered that the threaded hole function only as an intermediateexpediency and are of no final value. The foregoing burden is alsoapplicable to the machinist, who is concerned with only a single workpiece.

It would be highly advantageous therefore to provide improved workholding means.

Accordingly, it is an object of the instant invention to provide afixture for holding a work piece.

Another object of the invention is the provision of a fixture adaptedfor use with a machine tool to support a work piece during machiningoperations.

And, another object of the current invention is to provide a fixture ofthe plate type having various optional means for securing a work piecethereto.

Still another object of the invention is the provision of a work pieceholding fixture which is usable with a variety of machine tools.

Yet another object of the present invention is to provide a holdingfixture which is operatively usable with a work piece having preformedsecurment means.

A further object of the invention is the provision of a fixture which isself-aligning to compensate for inaccuracies of the securment means ofthe work piece.

Still a further object of this invention is to provide a work pieceholding device which is usable in prototype and production machiningsituations.

And yet a further object of the invention is the provision of a fixtureof the above type which is readily usable and durably constructed.

Briefly, to achieve the desired objectives of the present invention inaccordance with a preferred embodiment thereof, first provided is asubstantially rigid plate having first and second spaced opposedsurfaces. The first surface is considered the work bearing surface.Extending through the plate are a plurality of generally cylindricalbores each having a longitudinal axis substantially perpendicular to thework supporting face. A spindle is rotatably journalled within each borefor rotation about the longitudinal axis. Each spindle has a first end,which is positioned proximate the first surface of the plate. Retentionmeans are provided for limiting the actual movement of the spindle in adirection toward the first surface of the plate. Engagement receivingmeans are carried by each spindle for receiving means for securing thework piece against the work bearing surface of the plate.

Preferred engagement means carried by each spindle is in the form of aradial slot extending axially through the spindle. A bolt is receivablethrough the slot for engagement with a threaded hole preformed in thework piece and for securing the work piece to the work supportingsurface of the plate. The relative position of the slot, with referenceto the surface of the plate, is moveable in response to rotation of thespindle. The spindle may also carry other engagement receiving meanssuch as a T-slot extending diametrically across the end of the spindle.Preferably, the end of the spindle is recessed from the work supportingsurface of the plate to insure that the work piece abuts the worksupporting surface.

Alternate embodiments of the plate are adapted for use with variousmachine tools. In accordance with the foregoing embodiment, the plate isplaced horizontally upon the normal work supporting surface or table ofa machine tool. In an alternate embodiment, a second plate resting uponthe normal work supporting surface of the machine tool holds the worksupporting surface in vertical alignment.

In yet another embodiment, means are provided on the second surface ofthe plate for detachable securement to spindle type machines.

The foregoing and further and more specific objects and advantages ofthe present invention will become readily apparent to those skilled inthe art from the following detailed description of the invention andalternately preferred embodiments thereof taken in conjunction with thedrawings in which:

FIG. 1 is a perspective view of a work piece holding fixture constructedin accordance with the teachings of the present invention as it wouldappear when placed upon the normal work supporting table of a machinetool, such as a milling machine;

FIG. 2 is a perspective view generally corresponding to the view of FIG.1 and further illustrating the device of the present invention having awork piece supported thereby in position for machining;

FIG. 3 is an offset vertical sectional view taken along the line 3--3 ofFIG. 1;

FIG. 4 is an enlarged fragmentary view of the work supporting surface ofthe device of FIG. 1;

FIG. 5 is an enlarged fragmentary perspective view of the fixture ofFIG. 1 and shown partly in section as generated along the line 5--5 ofFIG. 4; and

FIG. 6 is an alternate embodiment of a work holding fixture constructedin accordance with the teachings of the present invention, andespecially adapted for use with spindle type machines, specificallyherein shown as a lathe.

Turning now to the drawings in which the same reference numeralsrepresent corresponding elements throughout the several views, attentionis first directed to FIG. 1 which shows a preferred embodiment of afixture in accordance with the instant invention and generallydesignated by the reference character 10. Fixture 10, as is also seen inFIG. 3, includes a substantially rigid plate 11 having first and secondspaced opposed surfaces 12 and 13. Plate 11 is generally rectangularhaving first and second longitudinal edges 16 and 17 respectively andfirst and second lateral edges 18 and 19 respectively. First surface 12is considered the work supporting surface, as will be describedpresently.

Rigid base plate 20 having top surface 21 and bottom surface 22 issecured to second surface 13 of plate 11 such as by mechanicalfasteners, welding or other expediencies well known in the metal workingart. Bottom surface 22 of base plate 20 is perpendicular to firstsurface 12 of plate 11.

Table 23 is representative of the typical work supporting table commonto various machine tools, such as milling machines for example. Table 23includes work supporting surface 26 having a plurality of parallellongitudinally extending T-slots 27. The use of T-slots 27 inconjunction with various clamping devices for affixing a work piecedirectly to work supporting surface 26, or alternately for securing anauxilliary work holding device, such as a vise or conventional angleplate, to surface 26 will be readily understood by those skilled in theart.

Surface 26 is a precision surface which is flat and generally eitherperpendicular or parallel to a cutting tool 28 rotated and held byspindle 29 of the machine tool as seen in FIG. 2. Bottom surface 22rests upon work supporting surface 26 and holds first surface 12 ofplate 11 in perpendicular alignment with surface 26. Rigidity isprovided by gusset 30 affixed to base 20 and plate 11 proximate secondlateral edge 19. Further rigidity is provided by end plate 31 similarlyaffixed to base 20 and plate 11 proximate first lateral edge 18. Inaccordance with the immediate embodiment, end plate 31 has an outsidesurface (not herein specifically illustrated) which is perpendicular tofirst surface 12 and to bottom surface 22. End plate 31 can be employed,similar to base plate 20 to rest upon work supporting surface 26 andsupport first surface 12 in a substantially vertical position. Variousmeans for rigidly attaching base plate 20 or end plate 31 to table 23will readily occur to those skilled in the art. For this purpose and toaccomodate bolts threadedly engageable with T-nuts carried withinT-slots 27, base plate 20 and end plate 31 may have apertures, either inthe form of cylindrical bores or slots, formed therethrough.

It will also be appreciated by those skilled in the art that, inaccordance with an alternate embodiment of the instant invention, plate11 is singularly useable without base 20, gusset 30 and end plate 31. Inthis configuration, plate 11 is placed horizontally and directly uponwork supporting surface 26. If it is desired to elevate plate 11 fromwork supporting surface 26, various types of well known spacers, such asthose commonly referred to as parallels, can be placed between worksupporting surface 26 and second surface 13 of plate 11. Plate 11 can besecured to table 23 by clamps or other well known means usuallyemploying the use of T-slots 27.

A plurality of spindles 32 are carried by plate 11. As clearly observedin FIG. 5, each spindle 32 has an outer cylindrical surface 33 which isrotatably journalled within a bore 34. Each bore 34 extends throughplate 33 between first surface 12 and second surface 13 and iscylindrical about a longitudinal axis shown by the broken line A, whichis perpendicular to face 12. Each spindle 32 is also rotatable aboutaxis A.

Each bore 34 includes a counterbore 37 extending inwardly from secondsurface 13 and terminating with annular shoulder 38 extending radiallybetween bore 34 and counterbore 37. Outer surface 33 of spindle 32comprises a first cylindrical section 39 and an enlarged secondcylindrical section 40 with annular shoulder 41 extending radiallytherebetween. First cylindrical section 39 and second cylindricalsection 40 are rotatable within bore 34 and counterbore 37 respectively.The contact between annular shoulder 38 and annular shoulder 41 providesretention means for limiting and axial movement of spindle 32 in adirection towards first surface 12, as indicated by arrow B.

Each spindle 32 has a first end 42 and a second end 43 each of which aregenerally perpendicular to axis A and which are positioned proximatefirst surface 12 and second surface 13 respectively of plate 12.Preferably, end 42 is recessed slightly, 5/1,000 of an inch for example,from first surface 12, the purpose of which will be explained presently.An annular groove 44 is formed in plate 11 extending radially outwardfrom counterbore 37. A lock ring 47, an annular member which is splitradially, resides within groove 44. Lock ring 47 extends radially inwardfrom counterbore 37 to receive second end 43 thereagainst and preventthe separation of spindle 32 from plate 11.

Referring now specifically to FIGS. 4 and 5, it is seen that eachspindle 32 is provided with various engagement receiving means forreceiving means for securing a work piece against surface 12 of plate11. First engagement receiving means is in the form of a slot 48. Slot48 extends through spindle 32, being open at first end 42 and second end43. Slot 48 also extends in a radial direction terminating at shoulder41 to be open with respect to first cylindrical section 39 and closedwith respect to second cylindrical section 40. Preferably, the inner end49 of slot 48 is semicylindrical about axis A. Accordingly, means forsecuring a work piece against first surface 12 can be received throughslot 48 at the center of spindle 32. If the securing means is a bolt,for example, the longitudinal axis of the bolt can align with axis A.The relative position of the bolt with respect to work supportingsurface 12 is readily alterable and determined by the axial placement ofthe bolt along slot 48 and the rotation of spindle 32. It will beappreciated therefore that the bolt is capable of assuming any positionwithin bore 34.

Second engagement receiving means carried by spindle 32 is in the formof a T-slot 50. T-slot 50 extends diametrically across spindle 32 and isopen at first end 42. Access to T-slot 50, for the insertion of a T-nutor T-headed bolt therein, is provided by an opening 51 havingsubstantially the same width as the enlarged portion of the T-slot andpositioned at approximate the axial center of spindle 32. It will bereadily recognized by those skilled in the art that T-slot 50, similarto slot 48, is moveable to provide engagement receiving means over theentire area defined by bore 34 in accordance with rotation of spindle32. A plurality of spaced threaded holes, such as formed by theoperations of drilling and tapping, are also carried by spindle 32 andform third engagement receiving means. Each threaded hole 52 extendssubstantially perpendicularly inward from first end 42.

Fixture 10 further includes fourth engagement receiving means which arecarried by a plate 11. Fourth engagement receiving means compriseslongitudinal T-slots 53 and lateral T-slots 54. T-slots 53 and 54 areaccessible from first surface 12 and are arranged to lie betweenspindles 32.

A typical work piece, such as work piece 57 shown in FIG. 2, can bereadily attached to fixture 10 by various means consistent with theimmediate desires of the machine tool operator. As previously stated, itis conventional practice to prepare the work piece by machining a basesurface and forming two or more threaded holes. With conventional angleplates or work holding fixtures, it was required that the threaded holesbe accurately placed to align with pre-existing bolt receiving holeswithin the angle plate. Alternately, the angle plate could be drilled toaccommodate a given work piece and threaded hole placement. It was alsonecessary that several fixtures be available for use in accordance withthe particular size and threaded hole placement of numerous and variouswork pieces, since it is obvious that a limited number of holes can bedrilled through a given fixture.

With the fixture of the instant invention, accurate placement of thethreaded holes in the base of the work piece is rendered unnecessary.The appropriate spindles are simply rotated until the slots 48 alignwith respective holes. This is particular important in the productionrun machining operations where locating means are used in combinationwith the holding fixture of the instant invention. The locating meansplaces each successive work piece at approximately the same location onface 12. Rotation of the appropriate spindles readily compensates forinaccuracies in the placement of threaded holes of subsequent workpieces.

Other obvious advantages are also accrued from the work holding fixtureof the instant invention. The use of various straps and clamps incombination with T-slots or threaded holes is conventional practice andwell known to those skilled in the art. Heretofore, the placement of theclamps or straps upon the work piece has been restricted in accordancewith the availability of T-slots or threaded apertures in a given workholding fixture. Frequently, it was necessary to clamp the work piece atavailable locations and machine that portion of the piece that wasexposed for machining. Subsequently, the work piece was reoriented andreclamped to make the remaining portions of the work piece to the cutterof the machine tool. With the device of the instant invention, it isreadily apparent that an infinite number of clamping positions areavailable between the combination of the T-slots 53 and 54 carried byplate 11, and the T-slots 50 and threaded holes 52 which are removeablein accordance with the rotating spindle 32.

As the bolt or other securing means is tightened, shoulder 38 is drawnfirmly against shoulder 41 and the base of the work piece is drawnfirmly against work holding surface 12. This is assured since first end42 of each spindle 32 is recessed from surface 12. During the securementof the work piece to face 12, no stress is applied to locking ring 43.

FIG. 6 illustrates an alternate embodiment of a work holding fixtureconstructed in accordance with the teachings of the instant inventionand generally designated by the reference character 60. Embodiment 60 isparticularly adapted for use in combination with the type of machinetool which rotates the work piece such as typically illustrated by lathe61. Briefly, lathe 61 includes bed 62 and head stock 63 which drivinglyrotates spindle 64. Further description of lathe 61 will not be made,since such machine tools are well known to those skilled in the art.

Work holding fixture 60 includes a generally cylindrical rigid plate 67having a work bearing first surface 68 and a spaced opposed secondsurface 69, the latter not being specifically visible. Plate 67 isgenerally analygous to plate 11 except for the parametric shape thereof.A plurality of spindles 32, as described in connection with the previousembodiment, are rotatably carried by plate 69. In the immediateembodiment, spindles 32 are placed annularly about work supporting face68.

Although not specifically herein illustrated, but as will be readilyunderstood by those skilled in the art, attachment means extend axiallyfrom second surface 69 for coupling fixture 69 with spindle 64.Manufacturers of lathes and other rotating type machine tools generallyprovide a variety of various work holding devices, such as face plates,chucks and collets, which are detachably secureable to the spindle ofthe machine in accordance with the immediate needs of the machineoperator. The exact means of attaching the work holding device to thespindle is variable with the specific manufacturer, but generallyincludes some type of threaded connection or pin and cam lockarrangement. The attachment means, as an independent accessory item, isoften supplied by the manufacturer for use by machine tool operatorsdesirous of fabricating a specialized work holding fixture. Such anaccessory is readily secureable to plate 67. Alternately, plate 67 canbe secured directly to a face plate as supplied by the manufacturer.

As illustrated herein, work piece 70 is being attached to fixture 60 forturning, boring and facing operations as are usually performed onlathes. Work piece 70 has been prepared by machining the base surface,if necessary, and forming threaded holes therein as appropriate.Subsequently, the base surface of work piece 70 is placed against workholding surface 68 of plate 67. Finally, bolts 71 are received throughslots 48 and secured with the threaded holes in work piece 70. A centeror other locating device may be used for placement of work piece 70 andthe appropriate spindles 32 rotated to bring the respective slots 48into alignment with the threaded holes in the work piece.

Various changes and modifications to the embodiments herein chosen forpurposes of illustration will readily occur to those skilled in the art.It is perceivable for example that the size, configuration, number andplacement of spindles within a given plate is at the discretion of themanufacturer. The number and placement of engagement and receiving meansassociated with each spindle is similarly readily alterable. Also,alternate shapes of the plate and the engagement receiving means carrieddirectly thereby are readily subject to modification. To the extent thatsuch modifications do not depart from the spirit and scope of theinvention, they are to be viewed in terms of the appended claims.

Having fully described and disclosed the present invention andalternately preferred embodiments thereof in such clear and conciseterms as to enable those skilled in the art to understand and practicethe same, the invention claimed is:
 1. A fixture for use with a machinetool and for holding a work piece during machining operation by saidmachine tool, said fixture comprising:(a) a substantially rigid platehaving first work supporting surface and a second spaced opposed surface(b) a generally cylindrical bore extending through said plate betweensaid first work supporting surface and second surface thereof; (c) aspindle having first and second ends and an outer generally cylindricalsurface and journaled within said bore for rotation about thelongitudinal axis of said bore, the first end of said spindle beingpositioned proximate but slightly recessed from the first worksupporting surface of said plate; (d) first retention means for limitingthe axial movement of said spindle in a direction toward the first worksupporting surface of said plate; and (e) engagement receiving meanscarried by said spindle for receiving means for securing said work pieceagainst the first work supporting surface of said plate.
 2. The fixtureof claim 1, wherein said first retention means includes:(a) a firstannular shoulder extending radially inward from said base; and (b) asecond annular shoulder extending radially outward from said spindle andreceived against said first shoulder.
 3. The fixture of claim 1, furtherincluding second retention means cooperating with said first retentionmeans for retaining said spindle within said bore.
 4. The fixture ofclaim 3, wherein said second retention means includes:(a) an annulargroove extending radially outward from said bore into said plate; and(b) an annular ring member carried in said groove and extending radiallyinward to receive the second end of said spindle thereagainst.
 5. Thefixture of claim 1, wherein said engagement receiving means comprises aradial slot extending through said spindle between the first and secondends thereof.
 6. The fixture of claim 5, wherein said slot extendsradially from proximate the center of said spindle to proximate theouter surface of said spindle.
 7. The fixture of claim 6, wherein saidslot defines an opening along the outer surfaces of said spindle.
 8. Thefixture of claim 1, wherein said engagement receiving means includes aT-slot extending diametrically along the first end of said spindle. 9.The fixture of claim 1, wherein said engagement receiving means includesan internally threaded bore extending inwardly from the first end ofsaid spindle and having a longitudinal axis substantially parallel tothe longitudinal axis of said spindle.
 10. The fixture of claim 9,further including a plurality of spaced, annularly arranged, internallythreaded bores extending inwardly from the first end of said spindle,each said bore having a longitudinal axis substantially parallel to thelongitudinal axis of said spindle.
 11. The fixture of claim 1, whereinthe first end of said spindle is recessed from the first surface of saidplate.
 12. The fixture of claim 1, further including engagementreceiving means carried by said plate.
 13. The fixture of claim 1,further including means for detachably securing said plate to saidmachine tool.
 14. The fixture of claim 1, wherein said plate isgenerally rectangular, having first and second longitudinal edges andfirst and second lateral edges.
 15. The fixture of claim 14, furtherincluding a first base plate carried by said rigid plate proximate alongitudinal edge thereof and having a bottom surface substantiallyperpendicular to the first surface of said rigid plate.
 16. The fixtureof claim 15, further including a second base plate carried by said rigidplate proximate a lateral edge thereof and having an outer surfacesubstantially perpendicular to the first surface of said rigid plate.17. The fixture of claim 1, wherein said rigid plate is generallycylindrical.
 18. The fixture of claim 17, further including meanscarried by the second surface of said rigid plate for attaching saidfixture to a machine tool.